Recent reports have indicated that the CNS may play an important role in the development and progression of endotoxin shock. Other reports indicate that capillary permeability dramatically increases in many vascular beds. This investigation proposes to use ventriculocisternal perfusion to detect any alterations in permeability of the ventricular system and of brain capillaries as well as to assess the cardiovascular effects of CSF borne hypotensive agents. The principle investigator is very familiar with the technique of ventriculocisternal perfusion. Although this technique has been used by other investigators, it has never been used to evaluate the shock state caused by endotoxin.